docs: Bring some order to filesystem documentation

2019-03-06T16:46:10Z

Documentation/filesystems is, like much of the rest of the kernel's documentation, a jumble of unorganized information. Split the documentation into categories and try to bring some order to the top-level index.rst files. No text changes other than a few section-introductory blurbs; this is all just moving stuff around. Cc: linux-fsdevel@vger.kernel.org Cc: Al Viro Signed-off-by: Jonathan Corbet

kernel/Documentation/filesystems/api-summary.rst, branch linux-5.1.y

docs: Bring some order to filesystem documentation